Tuesday, April 12, 2016

SCN8A mutation

Our genetics appointment has been moved up to April 19. I asked if there would be anything to actually report to us, since we don’t really need to go in just to hear “this test didn’t come up with anything new”.  She sent me the cover sheet of the test report, which is a little hard for me to interpret (thus I need to go to the appointment!) but it looks like Tessa has a mutation in a gene called SCN8A.

The report says “causative variant in disease gene associated with reported phenotype”. It is autosomal dominant, and she is heterozygous, which means one copy shows the phenotype. The mutation she has is de novo, meaning it happened spontaneously and was not inherited from me or Jeff.  The particular mutation she has (c.2890 G>C) is classified “likely pathogenic variant”, as opposed to “pathogenic” or “variant of unknown significance”. That is how much is on the report. The rest is courtesy of Doctor Google!

This gene makes a sodium channel that is mostly present on neurons in the cerebellum. From what I can tell, if you have a mutation that makes it more active, then you end up with a condition called EIEE13, which is a type of epilepsy, and if you have a mutation that makes it less active, then you end up with a condition called CIAT, which stands for Cognitive Impairment with or without cerebellar ATaxia.  CIAT symptoms include delayed cognitive, delayed motor, ADHD, uncoordinated gait, uncoordinated hands/arms, speech problems. The only symptom she doesn't have for this is crossed eyes.

Most of the stuff I have found online regarding SCN8A mutation relates to the epilepsy type, but even for that it seems pretty rare. Severity of symptoms seems to depend on how each mutation affects the protein function and there is a wide variety of the severity and type of symptoms. I do not see her particular mutation documented previously.  By my research, this mutation is in the middle of the helix of domain 2, subunit 6 of this protein which has 4 repeated domains of 6 subunits each, but I don’t know the significance of that yet.

Since most of this is what I have found on my own with google, this may not be what the doctor actually wants to tell me at all. I will have to find out when we go see her. But this is the latest on what is going on here!

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